Electronic transmission control systems for vehicles are generally well known in the art. In construction vehicles such control systems typically include manual and automatic modes of operation. In the manual mode, a transmission gear ratio is controlled in accordance with the position of a manual gear selector such as a gear shift handle or lever. Conversely, in the automatic mode, gear ratio is automatically controlled in accordance with a predetermined shiftpoint map which relates gear ratio to sensed operating parameters, such as vehicle speed and/or engine speed.
In many vehicles, it is desirable that the operator utilize the automatic shifting mode, thereby freeing his/her hands for controlling implement control levers, for example. However, often operators are forced to utilize the manual shifting mode because the preprogrammed shift points are inappropriate for operating conditions or due to operator preference.
Systems are available which make it possible to reprogram the factory shiftpoints using a service tool. However, such systems are undesirable because they require a special service tool and a trained technician to operate the service tool. Moreover, such systems result in excessive machine downtime because they don't permit the shiftpoints to be reprogrammed during vehicle operation.
Additionally, in the automotive field, it is known to provide a vehicle with two or more types of shifting patterns such as an economy shift pattern and a performance shift pattern. One such system is generally disclosed in U.S. Pat. No. 4,807,497 which issued on Feb. 28, 1989 to Yasue et al. However, such systems are limited in that they only provide preselected shiftpoint maps. As such, these systems are unable to adequately compensate for all changes in operating conditions.
The present invention is directed to overcoming the problems as set forth above.